The present invention relates to a swash plate type variable displacement compressor.
Japanese Laid-Open Patent Publications No. 5-172052 and No. 52-131204 disclose conventional swash plate type variable displacement type compressors (hereinafter, referred to as compressors). The compressors include a suction chamber, a discharge chamber, a swash plate chamber, and a plurality of cylinder bores, which are formed in a housing. A drive shaft is rotationally supported in the housing. The swash plate chamber accommodates a swash plate, which is rotatable through rotation of the drive shaft. A link mechanism, which allows change of the inclination angle of the swash plate, is arranged between the drive shaft and the swash plate. The inclination angle is defined with respect to a line perpendicular to the rotation axis of the drive shaft. Each of the cylinder bores accommodates a piston in a reciprocal manner and thus forms a compression chamber. A conversion mechanism reciprocates each of the pistons in the associated one of the cylinder bores by the stroke corresponding to the inclination angle of the swash plate through rotation of the swash plate. An actuator is capable of changing the inclination angle of the swash plate and controlled by a control mechanism.
In the compressor described in Japanese Laid-Open Patent Publication No. 5-172052, a pressure regulation chamber is formed in a rear housing member of the housing. A control pressure chamber is formed in a cylinder block, which is also a component of the housing, and communicates with the pressure regulation chamber. The actuator is arranged in the control pressure chamber, while being prevented from rotating integrally with the drive shaft. Specifically, the actuator has a non-rotational movable body that overlaps with a rear end portion of the drive shaft. The inner peripheral surface of the non-rotational movable body rotationally supports the rear end portion of the drive shaft. The non-rotational movable body is movable in the direction of the rotation axis of the drive shaft. The non-rotational movable body is slidable in the control pressure chamber through the outer peripheral surface of the non-rotational movable body and slides in the direction of the rotation axis of the drive shaft. The non-rotational movable body is restricted from sliding about the rotation axis of the drive shaft. A pressing spring, which urges the non-rotational movable body forward, is arranged in the control pressure chamber. The actuator has a movable body, which is joined to the swash plate and movable in the direction of the rotation axis of the drive shaft. A thrust bearing is arranged between the non-rotational movable body and the movable body. A pressure control valve, which changes the pressure in the control pressure chamber, is provided between the pressure regulation chamber and the discharge chamber. Through such change of the pressure in the control pressure chamber, the non-rotational movable body and the movable body are moved along the rotation axis.
The link mechanism has a movable body and a lug arm fixed to the drive shaft. A rear end portion of the lug arm has an elongated hole, which extends in a direction perpendicular to the rotation axis of the drive shaft from the side corresponding to the outer periphery of the drive shaft toward the rotation axis. A pin is received in the elongated hole and supports the swash plate at a position forward to the swash plate such that the swash plate is allowed to pivot about a first pivot axis. A front end portion of the movable body also has an elongated hole, which extends in the direction perpendicular to the rotation axis of the drive shaft from the side corresponding to the outer periphery of the drive shaft toward the rotation axis. A pin is passed through the elongated hole and supports the swash plate at the rear end of the swash plate such that the swash plate is allowed to pivot about a second pivot axis, which is parallel to the first pivot axis.
When a pressure regulation valve of the compressor is controlled to open, communication between the discharge chamber and the pressure regulation chamber is allowed. This raises the pressure in the control pressure chamber compared to the pressure in the swash plate chamber, thus causing the non-rotational movable body and the movable body to proceed. The inclination angle of the swash plate is thus increased and the stroke of each piston is increased correspondingly. This increases the displacement of the compressor per rotation cycle. In contrast, by controlling the pressure regulation valve to close, the communication between the discharge chamber and the pressure regulation chamber is blocked. This lowers the pressure in the control pressure chamber to a level equal to the pressure level in the swash plate chamber, thus causing the non-rotational movable body and the movable body to retreat. The inclination angle of the swash plate is thus decreased and the piston stroke is decreased correspondingly. This decreases the displacement of the compressor per rotation cycle.
In the compressor disclosed in Japanese Laid-Open Patent Publication No. 52-131204, an actuator is arranged in a swash plate chamber in a manner rotatable integrally with a drive shaft. Specifically, the actuator has a rotation body rotating integrally with the drive shaft. The interior of the rotation body accommodates a movable body, which moves in the direction of the rotation axis of the drive shaft and is movable relative to the rotation body. A control pressure chamber, which moves the movable body using the pressure in the control pressure chamber, is formed between the rotation body and the movable body. A communication passage, which communicates with the control pressure chamber, is formed in the drive shaft. A pressure control valve is arranged between the communication passage and a discharge chamber. The pressure control valve changes the pressure in the control pressure chamber to allow the movable body to move in the direction of the rotation axis relative to the rotation body. The rear end of the movable body is held in contact with a hinge ball. The hinge ball is joined to a swash plate to allow the swash plate to pivot. A pressing spring, which urges the hinge ball in such a direction as to increase the inclination angle of the swash plate, is arranged at the rear end of the hinge ball.
A link mechanism includes the hinge ball and a link arranged between the rotation body and the swash plate. A pin perpendicular to the rotation axis of the drive shaft is passed through the front end of the link. Another pin perpendicular to the rotation axis of the drive shaft is inserted through the rear end of the link. The link and the two pins support the swash plate to allow the swash plate to pivot in the housing.
When a pressure regulation valve of the compressor is controlled to open, communication between a discharge chamber and a pressure regulation chamber is allowed. This raises the pressure in the control pressure chamber compared to the pressure in a swash plate chamber, thus causing the movable body to retreat. The inclination angle of the swash plate is thus decreased and the stroke of each piston is decreased correspondingly. This reduces the displacement of the compressor per rotation cycle. In contrast, by controlling the pressure regulation valve to close, the communication between the discharge chamber and the pressure regulation chamber is blocked. This lowers the pressure in the control pressure chamber to a level equal to the pressure level in the swash plate chamber, thus causing the movable body to proceed. The inclination angle of the swash plate is thus increased and the piston stroke is increased correspondingly. This increases the displacement of the compressor per rotation cycle.
However, the compressor described in Japanese Laid-Open Patent Publication No. 5-172052 is elongated as a whole in the axial direction due to the non-rotational movable body of the actuator, which moves in the direction of the rotation axis in the rear end portion of the drive shaft.
Additionally, in this compressor, the non-rotational movable body of the actuator rotationally slides on the inner peripheral surface of the non-rotational movable body. Also, the non-rotational movable body moves in the direction of the rotation axis of the drive shaft on the inner peripheral surface and the outer peripheral surface of the non-rotational movable body. This may cause insufficient lubrication about the non-rotational movable body, thus lowering the sliding performance of the actuator. As a result, the inclination angle of the swash plate may not be changed in a favorable manner, thus hampering desirable displacement control performed by selectively increasing and decreasing the piston stroke. Also, in the compressor, wear may occur in the actuator and the vicinity thereof and thus the durability of the compressor may be lowered.
In the compressor described in Japanese Laid-Open Patent Publication No. 52-131204, the actuator is arranged in the vicinity of the rotation axis of the drive shaft compared to the link of the link mechanism. This limits the radial dimension of the control pressure chamber of the actuator, thus making it difficult for the movable body to urge the swash plate. Additionally, the link mechanism of the compressor may hamper lubricant supply to the actuator and such insufficient lubrication may lower the sliding performance of the actuator. This makes it difficult to change the inclination angle of the swash plate of the compressor in a favorable manner, thus hampering desirable displacement control.